04 CRF to k5

[cmotodad]

In the process of putting an 89 K5 into an 04 crf 250 chassis.Has anyone built one of these? If so, how was it to build? Thanks, Bob

[81cr450]

I've done a gen2 & gen3 cr250r chassis with a k5 motor. Pretty easy, you dont have to cut the Y. Hardest bit is the case milling to narrow it enough to fit between swing arm bearing carriers.

heres a link to the build, any questions feel free to ask

 http://www.kxriders.com/forums/index.php/topic,9339.0.html

I believe your F frame should be the same as the R frame both would be gen 3

[ZETTNORCAL]

you will have to cut the y on the f frame for sure.

[cmotodad]

If have built a crf250/500 honda, a cr125/500 Honda and a cr250/500 Honda. Have cut Y's, made solid billet y's and mounts. The Y will move up just like a CR5. I think all 3 chassis used the same Honda spacers. The only part that has me worried is the centering of motor and the clearancing of swingarm. Any and all help on how much to mill to center is apreciated. 81 cr450, did you get my pm?

[81cr450]

My thought is why cut the Y if you dont have to? The K5 motor is near an inch shorter than the cr & lighter to boot. I havent looked at an F frame there though just assuming

You narrow the case on both builds , didnt write it down the first time though. the swinger on the first one wasnt clearanced as it was narrower on the pivot points. I'm thinking I took off the same on the other case but it was more from the opposite side of the case, like exactly backwards

[cmotodad]

You definately need to raise the Y on the F.The F has a good part to remove, clean and reweld. I will make some billet front mounts and rails with inserts to match the existing rails and Y. I will do the measuring and keep a log.

[cmotodad]

Well, it was a good night in the garage. The engine is now 17mm swingarm size and the cases have been narrowed to fit the swingarm and center the countershaft sprocket. I took 1mm off the countershaft side to make the sprocket alignment. After the 1mm was removed, I measured the swingarm width using 2 countershaft side swingarm spacers from a CRF250, one on each side and then removed @ 3mm from the brake side. No narrowing of spacers and stock parts. Nice fit with perfect sprocket alignment. I will keep updates as I progress.

[cmotodad]

Spent more time in the garage. The frame is cut, Y raised and extensions in place. Milled up some lower motor mounts, made the headstay brackets and fabbed up some removable front motor mounts. Project is coming along nicely. I have the plate made for the airbox but I am trying to decide on the best boot. CR250 is close, stock 500 is close but I think I will look for a 2003 KX250 boot. After the welding is complete, I will get my son to help me post some photos.

[cmotodad]

Here are the photos of the raised Y, motor mounts, ignition bracket, and coil mount. More to come...

[cmotodad]

It's been awhile but I spent a little time on the conversion. Doing a little test fitting and now have the Fluidyne radiators welded for the K5 motor. It took 2 new 90,s for the lower crossover, 2 plugs on the stock lower crossovers and a new 90 for the line to the w/p. Went to the auto parts store and found a hose from the head to rad, a stock K5 works to the w/p and a straight lower crossover hose with the stock CRF250 upper. Most of the fitment is complete just waiting for the crank from Crankwerks and will be ready to assemble the motor and install.

[cmotodad]

Well, I finally received the balanced crank. Now I need to get time to assemble the motor. I am debating on having someone do the cylinder. Looking for a smooth motor to use for mx. Any opinions? Thanks

[sandblaster]

Looks great!
Your tearing this build up!

[sandmaster995]

Wow.....That is some clean work. Impressive.

[cmotodad]

Well, my buddy called today and said come over and take a look at the AF pipe. WOW! He used the head pipe from the PC pipe (like the old works pipe I have seen) and then formed a proper dimension cone pipe out to the CR500 silencer. I am so ready to get it together now. I am getting new mounts and he will place the mounts and it will be ready. Pics when I figure out how to get it from my phone to computer.

[cmotodad]

Here is the photo of almost complete pipe. Sorry, I cannot move it from my pictures to this post.